Brief Description

Foster® 65-05 WB Mastic is a high-quality, fibrated, water-based mastic. It is known for its bright white color and extremely smooth, creamy, and thixotropic consistency, facilitating fast and easy application. This mastic forms a tough, fire-resistive, and flexible dry film, providing a smooth, attractive finish suitable for both indoor and outdoor applications.

Key Specifications and Properties

• Color and Consistency: Bright white, extremely smooth, and creamy thixotropic consistency.
• Application Properties: Excellent for brush, trowel, and spray applications; non-flammable when wet with a mild odor during application.
• Flexibility and Finish: Forms a tough, fire-resistive, flexible dry film, offering a smooth and attractive finish.
• Adhesion: Excellent adhesion to most foil facings, suitable for a variety of thermal insulations including polystyrene and rigid polyurethane board stock insulations.

Certifications and Standards

• Underwriters Laboratories Inc.: Classified and followed-up by UL.
• NFPA Standards: Meets NFPA 90A and 90B 25/50 requirements.
• Environmental and Health Standards:
  • MAS Certified Green®
  • California Dept. of Public Health Standard Method v1.2
  • Contributes to LEED v4 EQ Credit: Low Emitting Materials – Paints and Coatings
  • Compliant with Collaborative for High Performance Schools EQ 7.1

Application and Limitations

• Temperature Range: Apply between 40ºF (4ºC) and 100ºF (38ºC); protect from freezing until dry.
• Drying Time: Allow at least 24 hours above 60ºF (16ºC) with 50% relative humidity to resist rain washoff.
• Surface Preparation: Do not thin; apply to clean, dry, oil-free surfaces without stirring.
• Outdoor Use: Ensure outdoor horizontal surfaces drain completely; a pitch of at least 1/2 inch per foot (4 cm/m) is required.
• Color Selection: Select white color for use over polystyrene in outdoor installations.

Application Techniques

• Trowel: Use a clean steel trowel for full-thickness application, avoiding excessive troweling.
• Brush: Suitable for water-based paints; apply with full brush and spread evenly without overworking. Multiple coats might be needed.
• Spray: Airless spray application possible; consult Airless Spray Recommendations for equipment details.

Cleanup and Maintenance

• Use fresh water to clean brushes and equipment before the product dries.
• For dried product, use hot soapy water or strong solvents like chlorinated solvent (non-flammable) or xylol (flammable)